Hydrogen in n-type diamond

The incorporation of hydrogen in n-type diamond has been investigated through its non-intentional introduction during the growth and through post U-growth diffusion experiments. In the first case, (I 11) n-type diamond homoepitaxial films doped with phosphorus have been grown by microwave plasma chemical vapor deposition from a CH4+D-2 mixture. The phosphorus concentrations were in the range 1.3 x 10(18)-3 x 10(19) cm(-3). The concentration of deuterium incorporated is usually 100 times below the phosphorus concentration, which indicates an absence of donor passivation by hydrogen in these films. These D concentrations are well below the H concentration of 10(21) cm(-3) reported in undoped (I 11) homoepitaxial diamond films. Exposures of phosphorus-doped and of nitrogen-doped diamonds to deuterium plasma show an absence of deuterium diffusion, even at elevated temperatures (1000 degreesC). The high migration energy of H-, combined with strong H-donor interactions and self-trapping of hydrogen, are possible reasons for the absence of significant hydrogen diffusion. In natural type la diamonds, a hydrogen-related vibrational band is very frequently observed at 3107 cm(-1). From the similarity of some properties of this band and of the bands related to well identified (H, impurity) complexes in conventional semiconductors, we propose that (N,H) complexes are responsible for this absorption band. (C) 2002 Elsevier Science B.V. All rights reserved.